Effective voltage stabilizer

ABSTRACT

An effective-voltage stabilizer including an output transistor for switching an input DC voltage, the stabilizer comprising a charging - discharging circuit connected to the output side of said output transistor and consisting of a capacitor and resistors, and a switching controlling circuit for detecting a voltage appearing across the capacitor in said charging discharging circuit and on-off controlling said output transistor according to the detected voltage, thereby generating a squarewave output from said output transistor and stabilizing the effective-voltage of said square-wave output.

United States Patent [19 Kawashima [75] Inventor:

[73] Assignee: Nippondenso Co., Ltd., Kariya-shi, Aichi-ken, Japan 22Filed:. noo.12,1972

211 Appl. No.: 314,456

30 Foreign Application Priority. Data 3,571,626 3/1971 Reif .fi 307/2903,582,762 6/1971 Mori 317/234 H 3,671,852 6/1972 Ritzenthaier 307/2973,707,635 12/1972 Kawashima 307/297 Primary Examiner Andrew J. JamesAttorney, Agent, or FirmCushman, Darby &

Cushman [57] ABSTRACT Dec. 14, 1971 Japan 46-101718 An effectivewoltgestabilizer including an output transistor for switching an input DCvoltage, the stabi- [52] US. C1 307/297, 307/234, lizer comprising acharging discharging circuit com Int CI p 3 03k v nected to the outputside of said output transistor and l consisting ofa capacitor andresistors and a switching [58] Flew of Search 7 2515 3 controllingcircuit for detecting a voltage appearing across the ca acitor in saidchar 'n dischar in cir- P 3 g g g cuit and on-off controlling saidoutput transistor ac- {561 References cued cording'to the detectedvoltage, thereby generating 21 UNITED STATES PATENTS square-wave outputfrom said output transistor and 3,265,956 8/1966 Schlabach.....- 308/297X stabilizing the effective-voltage of said square-wave 3,286,15711/1966 output. 3,321,698 5/1967 3,368,139 2/1968 Wuerflein 307/297 x 8Claims, 7 Drawing Figures PATENTEDAPRBU mm SHEET 1. OF 2 F I I PRIOR ARTI &3 5 71:1 8 5 FIG. 2 PRICXR ART EFFECTIVE VOLTAGE STABILI'ZER FIELD OFTHE INVENTION This invention relates to a voltage stabilizer and moreparticularly to an effective-voltage regulator for generating asquare-wave output which has a regulated effective-voltage.

SUMMARY OF THE INVENTION An object of the present invention is toprovide a voltage stabilizer in which the effective-voltage of asquare-wave output is controlled constant and hence the powerconsumption in an output transistor for controlling an input voltage isdecreased.

Another object of the present invention is to provide a voltagestabilizer which is easily fabricated in an IC circuit form and havelong service life.

A further object of the present invention is toprovide a voltagestabilizer capable of stabilizing the effectivevoltage of a square-waveoutput with practical accuracy.

According to an embodiment of the present invention, there is providedan effective-voltage stabilizer comprising an output transistor foron-off controlling an input voltage to generate a square-wave output, an

output voltage compensating circuit for voltagecompensating, theeffective-voltage of said squarewave output to be constant by generatinga compensating voltage across a capacitor, and a switching circuit fordetecting a voltage across said capacitor and on-off controlling saidoutput transistor. v

Other objects, features and advantages of the present invention willbecome apparent from the following detailed description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electrical circuitdiagram of a conventional bimetal-type voltage stabilizer.

FIG. 2 is an electrical circuit diagram of a conventionaltransistor-type voltage stabilizer used in a meter.

FIG. 3 is an electrical circuit diagram of an embodiment of the presentinvention.

FIG. 4 is an electrical circuit diagram to be used for comparison to thepresent invention.

FIG. 5 is a schematic electrical connection diagram of the-presentdevice to be used in the description of the effective-voltage of asquare-wave output according to the present device.

FIG. 6 is a diagram of an output voltage waveform to be used in thedescription of the present invention.

FIG. 7 is an experimental characteristic curve of an example of thepresent device.

In the figures, similar reference numerals indicate similar orequivalent parts.

DESCRIPTION OF THE PREFERRED EMBODIMENT Description is first made onvoltage stabilizers according to the prior art for facilitating theunderstanding of the present invention.

FIG. 1 shows a simple bimetal-type voltage regulator indicated in blockA, which comprises contacts 1, a bimetal strip 2, a heater wire 3, aresistance wire 4, an indicator formed of a bimetal strip 5, athermistor 6, an

input terminal 7, an output terminal 8, and a grounded terminal 9.Output is derived from the output terminal 8. Voltage regulators of thistype have such a drawback that they often cause malfunction and havepoor service life. There have been also proposed transistortype voltagestabilizers in which said contacts 1 are reformed or modified incontactless continuous type, such as shown in FIG. 2. The voltagestabilizer shown in FIG. 2 comprises a transistor 10, a resistor 11, aZener diode 12, and a diode 13. An output is derived from the outputterminal 8. Voltage stabilizers of this type have such a drawback thatthe power consumption in the transistor 10 is large and thus requires alarger power transistor which increases costs.

Now, description isrnade on the embodiment of the present inventionshown in the drawings.

In the embodiment of FIG. 3, a voltage stabilizer (regulator) isindicated by A and includes a switching circuit B and a constant currentcircuit C for stabilizing an input current of the switching circuit B.The constant current circuit C consists of a resistor 14, a Zener diode15, and a transistor 16. An output transistor circuit 10 consists of aDarlington connection of two transistors 10a and 17 and is controlled bythe circuit consisting of a Darlington connection of two transistors 18and '19. Numerals 20 and 21 are biassing resistors. A I

level shifting circuit D is formed of level-shifting diodes 22,23 and 24and a transistor 25. A switching voltage detecting circuit E is formedof a Schmitt circuit comprising two transistors 27.and 28, two collectorresistors 26 and 29, and a common emitter resistor 30. Further, atemperature compensating circuit F is formed of a transistor 32 providedwith an emitter resistor 31, two diodes 33 and 34, and two biasresistors 35 and 36. An impedance transforming circuit G for detectingvoltage G is formed of a Darlington connection of two transistors 37 and38 provided with an emitter resistance 39, and forms an emittenfollowercircuit for the abovementioned Schmitt circuit. An output voltagecompensating circuit H is formed of a diode 40, four resistors 41, 42,43 and 44, and a capacitor 45. Here, the switching circuit B can beformed by various methods.

The operation of the present device will be described with respect tothe above structure. A charging current is allowed to flow by a voltageappearing at the output terminal 8 through the diode 40 and the resistor41 in the output voltage compensating circuit H to the capacitor 45.When the voltage of this capacitor 45 reaches a predetermined value, thetransistor 28 of the switching voltage detecting circuit E becomesconductive and this transistor 27 becomes of a high level, i.e., itscut-off state. Then, through the level shifting circuit D including thethree diodes 22, 23 and 24 and the transistor 25, the voltage at theinterconnection of the resistors 20 and 21 is increased and thetransistors 18 and 19 connected in Darlington connection are turned intotheir conductive states. Thus, the output transistor circuit 10 isrendered to be cut off.

When the output transistor circuit 10 is cut off, the voltage at theoutput terminal 8 becomes zero. Then, in the output voltage compensatingcircuit the capacitor 45 discharges through two resistors 42 and 43.When the voltage across the capacitor 45 decreases below a predeterminedvalue, said switching voltage detecting circuit E is reversed and theoutput transistor circuit 10 returns to the conductive state.

The above cycle is repeated. Thus, a DC voltage applied to the inputterminal 7 is transformed into a square-wave output having a stabilizedeffective voltage, which operates the load resistor 4, the indicator 5formed of a bimetal strip and the thermistor 6, with high precision.

Further, the line voltage (power source voltage) for said switchingvoltage detecting circuit E is fixed by the constant current circuit Ccomprising the resistor 14, the Zener diode l5 and the transistor 16.Therefore, it does not vary even when a DC voltage applied between theterminals 7 and 9 is varied. Further, the temperature compensation ofthis switching voltage detecting circuit E can be achieved by thetemperature compensating circuit F in which the forward voltage drop ofthe two diodes 33 and 34 varies depending on the temperature and hencethe base current of the transistor 32 is varied to achieve thetemperature compensation. Further, the emitter-follower circuit Gcomprising two transistors 37 and 38 and the emitter resistor 39 functions to isolate the impedance on the Schmitt circuit side from that onthe output voltage compensating circuit side and accordingly, theimpedance on the switching voltage detecting circuit E side does notinfluence the charging and discharging time constant of the capacitor 45in the output voltage compensating circuit I-I.

Next, the constancy of the effective-voltage of the square-wave outputwill be discussed in detail referring to the electrical connectiondiagram of FIG 5 of the present voltage stabilizer provided with anoutput voltage compensating circuit 1-! in comparison to the elec tricalconnection diagram of FIG. 4. The effectivevoltage of the presentvoltage stabilizer will be calculated. It is assumed that the voltagebetween input terminals'7 and 9 is V (volts), the resistances of thefive resistors 41, 42, 43, 44 and 47 are R (ohms), r1 (ohms), r2 (ohms),p (ohms) and r (ohms), the capacitance of the capacitor 45 is C(Farads), that the switching circuit B drives the output transistorcircuit to be cut off when the voltage at a terminal 48 is V,, (volts)and to be conductive when the voltage at the terminal 48 is (V, AV), andthat V, AV and the saturation voltage of the output transistor 10 andthe voltage drop in the diode 40 are negligible First, theefi'ective-voltage at the terminal 8 of the voltage stabilizer of FIG. 4Val is calculated. If the time periods during which the outputtransistor circuit 10 is conductive andcut ofiare set t and t as shownin the output voltage waveform of FIG. 6, respectively,

The charging current I flowing into the capacitor 45 when the voltage atthe terminal 48 is in the neighborhood of V, is

provided that the output, transistor circuit 10 is conductive. Further,the discharging current I flowing from the capacitor 45 when the outputtransistor circuit 10 is cut off, is'

provided that a resistor of a sufficiently small resistance compared to.R is connected between the terminals 8 and 9. Here, 1 and t are thetime periods required for the voltage at the terminal 45 to rise from V,A V) to V and to drop from V,, to (V AV) by the charge and discharge ofthe capacitor 45. In this case, AV is sufi'iciently small in comparisonto V and thus a (V0 cl' am 1 AV- C/I,

Further,

t AV-C/I I s From equations 2, 3, 4 and 5, equation 1 becomes V g VI /Ii- (6) Thus, in the output voltage controlling circuit of FIG. 4 whenthe input voltage is changed, the output effective-voltage V is alsovaried and the output squarewave does not have a stabilizedeffective-voltage.

Next, the effective-voltage of the square-wave output appearing at theoutput terminal 8 in the output voltagecompensating circuit of FIG. 5 Vis calculated in the similar manner. When the voltage at the terminal 48is in the neighborhood of V and the output transistor circuit 10 isconductive, the charging current I flowing into the capacitor 45 is fo)/ [(m p)' n "2' l/ 1' a (n- The discharging current 1, 5 flowing fromthe capacitor 45 when the output transistor circuit 10 is cut off, is

1, [(r +p)' V,,r 'V]/[r,'r +(r +r p] 3 W= o a) V2 Differentiation of Wwith respect to V gives dW/dV= o) 0 Thus, W has a flexion point at V 3V,,.

In the neighborhood of V 3V,, the variation of W is extremely small andthe effective-voltage of the squareoutput efiective-voltage V becamealmost constant. This range corresponds to the practical range of theeffective-voltage stabilizer of the present example.

According to this effective-voltage stabilizer, a contactless transistortype voltage stabilizer capable of providing a square-wave output can beachieved, power consumption in a transistor can be decreased to reducethe cost, and loads such as a meter connected to this stabilizer can beoperated with high precision by stabilizing the effective-voltage of thesquare-wave output.

I claim:

1. An effective-voltage stabilizer device comprising input terminalmeans for receiving an input voltage, output terminal means forconnection to a load, an output transistor circuit coupling the inputterminal means to the output terminal means, said output transistorcircuit having a control input and having a conductive and anon-conductive condition responsive to said control input, an outputvoltage compensating circuit coupled to said output terminal means, saidoutput voltage compensating circuit including a capacitor adapted tocharge through said output transistor circuit when said outputtransistor circuit is in a conductive state and to discharge when saidoutputtransistor circuit is in said non-conductive state, and aswitching controlling circuitresponsive to the state of chargeon saidcapacitor for generating a switching control signal, coupling means forcoupling said switching control signal to said control input of saidoutput transistor circuit for controlling the conductive state thereof,and in which said output voltage compensating circuit includes a seriesresistance circuit connected in parallel across said capacitor, inseries connection circuit of a diode and a resistor, connected betweenthe output terminal means and said series resistance, and a resistorconnected between one connection point in said series resistance circuitand the input terminal means.

2. An effective-voltage stabilizer device according to claim 1, in whichsaid series resistance circuit comprises a series connection of firstand second resistors, and in which the resistance of said resistorconnected in series with said-diode between the output terminal meansbeing relatively large compared to that of the load, and the resistanceof the'resistor connected between one connection point in said seriesresistance circuit and the input terminal means being larger than that4. An effective-voltage stabilizer device according to claim 3,including an emitter follower circuit and in which said emitter followercircuit is connected between said capacitor and said Schmitt circuit formaintaining the time constant of charging or discharging of saidcapacitor constant. I

5. An effective-voltage stabilizer device according to claim 3,including a constant current source provided between said input terminalmeans and said output transistor circuit and in which said constantcurrent source is coupled to said switching controlling circuit forsupplying an output voltage to said switching controlling circuit as thepower voltage source.

6. An effective-voltage stabilizer device according to claim 1, in whichsaid output transistor circuit includes a Darlington circuit.

7. A constant effective-voltage power source circuit comprising aconstant current circuit, an output transistor circuit connected to saidconstant current circuit for on-off controlling an input voltage, anoutput voltage compensating circuit connected to both .said constantcurrent circuit and said output transistor circuit, a switching circuitconnected to said output voltage compensating circuit for controllingthe on-off state of said transistor circuit according to a voltageestablished in said compensating circuit, and output terminals connectedto said compensating circuit whereon the effective voltage across saidoutput terminals is maintained substantially constant.

8. A constant effective-voltage power source circuit according to claim7, in which said output voltage compensating circuit comprises acapacitor, a series resistance circuit connected in parallel across saidcapacitor, a series connection circuit of a diode and a resistor,connected between the output side of said output semiconductor circuitand series resistance circuit, and a resistor connected between oneconnection point in said series resistance circuit and the'input side ofsaid output semiconductor circuit.

1. An effective-voltage stabilizer device comprising input terminalmeans for receiving an input voltage, output terminal means forconnection to a load, an output transistor circuit coupling the inputterminal means to the output terminal means, said output transistorcircuit having a control input and having a conductive and anon-conductive condition responsive to said control input, an outputvoltage compensating circuit coupled to said output terminal means, saidoutput voltage compensating circuit including a capacitor adapted tocharge through said output transistor circuit when said outputtransistor circuit is in a conductive state and to discharge when saidoutput transistor circuit is in said non-conductive state, and aswitching controlling circuit responsive to the state of charge on saidcapacitor for generating a switching control signal, coupling means forcoupling said switching control signal to said control input of saidoutput transistor circuit for controlling the conductive state thereof,and in which said output voltage compensating circuit includes a seriesresistance circuit connected in parallel across said capacitor, inseries connection circuit of a diode and a resistor, connected betweenthe output terminal means and said series resistance, and a resistorconnected between one connection point in said series resistance circuitand the input terminal means.
 2. An effective-voltage stabilizer deviceaccording to claim 1, in which said series resistance circuit comprisesa series connection of first and second resistors, and in which theresistance of said resistor connected in series with said diode betweenthe output terminal means being relatively large compared to that of theload, and the resistance of the resistor connected between oneconnection point in said series resistance circuit and the inputterminal means being larger than that of the second resistor.
 3. Aneffective-voltage stabilizer device according to claim 1, in which saidswitching controlling circuit includes a Schmitt circuit for generatinga binary signal corresponding to the charging and discharging level ofsaid capacitor.
 4. An effective-voltage stabilizer device according toclaim 3, including an emitter follower circuit and in which said emitterfollower circuit is connected between said capacitor and said Schmittcircuit for maintaining the time constant of charging or discharging ofsaid capacitor constant.
 5. An effective-voltage stabilizer deviceaccording to claim 3, including a constant current source providedbetween said input terminal means and said output transistor circuit andin which said constant current source is coupled to said switchingcontrolling circuit for supplying an output voltage to said switchingcontrolling circuit as the power voltage source.
 6. An effective-voltagestabilizer device according to claim 1, in which said output transistorcircuit includes a Darlington circuit.
 7. A constant effective-voltagepower source circuit comprising a constant current circuit, an outputtransistor circuit connected to said constant current circuit for on-offcontrolling an input voltage, an output voltage compensating circuitconnected to both said constant current circuit and said outputtransistor circuit, a switching circuit connected to said output voltagecompensating circuit for controlling the on-off state of said transistorcircuit according to a voltage established in said compensating circuit,and output terminals connected to said compensating circuit whereon theeffective voltage across said output terminals is maintainedsubstantially constant.
 8. A constant effective-voltage power sourcecircuit according to claim 7, in which said output voltage compensatingcircuit comprises a capacitor, a series resistance circuit connected inparallel across said capacitor, A series connection circuit of a diodeand a resistor, connected between the output side of said outputsemiconductor circuit and series resistance circuit, and a resistorconnected between one connection point in said series resistance circuitand the input side of said output semiconductor circuit.